Electronic circuitry can be sensitive to variations in power supply voltage. Thus, a regulated power supply can be used to provide operating energy for the electronic circuitry by regulating or adjusting an input power signal to provide output power within a specified output voltage range. A regulated power supply can include a DC-DC regulator. In an example, the DC-DC regulator can receive a DC input and provide a regulated, relatively stable DC output across different load conditions, including sudden or transient changes in load current.
In certain power supplies, feedback can be used to help maintain the output voltage within the specified range. In an example, a “linear” regulator can include a shunt or series transistor operating in a partially conductive or linear region to modulate a current supplied by the regulator, such as in response to changing load conditions. In certain examples, the transistor can be controlled by feedback circuitry, such as one or more operational amplifiers, to further improve the transient response and regulation performance of the regulator. In the linear regulator, excess current not needed by the load can be diverted away from the load and dissipated elsewhere (e.g., as heat). The linear regulator can thus achieve reasonable levels of regulation performance, but at relatively high costs in terms of size, complexity, or efficiency, compared other regulators, such as a switched-mode regulator. For example, in a linear regulator, the series or shunt transistor must be able to operate continuously at the maximum rated supply current of the regulator, necessitating a relatively large shunt or series transistor as compared to correspondingly-rated switched-mode supply.